Accounting for inertial measurement unit bias

Abstract

Techniques for accounting for rotational bias of an inertial measurement unit in a setting where momentum is conserved are presented. The techniques include: obtaining, from an inertial measurement unit, an initial magnitude of momentum and initial directional rotational rates; iteratively updating an estimate of bias of magnitude of momentum and estimates of bias of directional rotational rates based at least on the obtaining and based at least on readings from the inertial measurement unit; adjusting directional rotational rates obtained from the inertial measurement unit to account for the estimates of bias of directional rotational rates, where bias adjusted directional rotational rates are determined; and providing the bias adjusted directional rotation rates.

What is claimed is: 
     
         1 . A method of accounting for rotational bias of an inertial measurement unit in a setting where momentum is conserved, the method comprising:
 obtaining, from the inertial measurement unit, an initial magnitude of momentum and initial directional rotational rates;   iteratively updating an estimate of bias of magnitude of momentum and estimates of bias of directional rotational rates based at least on the obtaining and based at least on readings from the inertial measurement unit;   adjusting directional rotational rates obtained from the inertial measurement unit to account for the estimates of bias of directional rotational rates, wherein bias adjusted directional rotational rates are determined; and   providing the bias adjusted directional rotation rates.   
     
     
         2 . The method of  claim 1 , wherein the setting comprises a micro gravity or zero gravity environment, and wherein a vehicle in the setting comprises the inertial measurement unit. 
     
     
         3 . The method of  claim 2 , further comprising changing an attitude of the vehicle based on the bias adjusted directional rotational rates. 
     
     
         4 . The method of  claim 3 , wherein the changing comprises activating a thruster of the vehicle. 
     
     
         5 . The method of  claim 1 , wherein the estimate of bias of magnitude of momentum and the estimates of bias of directional rotational rates are further based on outputs of an internal momentum storage device. 
     
     
         6 . The method of  claim 1 , wherein the inertial measurement unit comprises a micro electro-mechanical inertial measurement unit. 
     
     
         7 . The method of  claim 1 , wherein the iteratively updating comprises iteratively updating using a Kalman filter. 
     
     
         8 . The method of  claim 1 , wherein the iteratively updating, the adjusting, and the providing are performed in real time. 
     
     
         9 . The method of  claim 1 , wherein the directional rotational rates comprise three-dimensional directional rotational rates. 
     
     
         10 . The method of  claim 1 , wherein the iteratively updating comprises iteratively updating using one of: a fixed gain filter, a batch filter, recursive least squares, H-infinity control, or moving horizon estimation. 
     
     
         11 . A system accounting for rotational bias of an inertial measurement unit in a setting where momentum is conserved, the system comprising:
 the inertial measurement unit;   an electronic processor; and   persistent non-transitory storage including instructions that, when executed by the electronic processor, configure the electronic processor to perform actions comprising:
 obtaining, from the inertial measurement unit, an initial magnitude of momentum and initial directional rotational rates; 
 iteratively updating an estimate of bias of magnitude of momentum and estimates of bias of directional rotational rates based at least on the obtaining and based at least on readings from the inertial measurement unit; 
 adjusting directional rotational rates obtained from the inertial measurement unit to account for the estimates of bias of directional rotational rates, wherein bias adjusted directional rotational rates are determined; and 
 providing the bias adjusted directional rotation rates. 
   
     
     
         12 . The system of  claim 11 , wherein the setting comprises a micro gravity or zero gravity environment, and wherein a vehicle in the setting comprises the inertial measurement unit. 
     
     
         13 . The system of  claim 12 , wherein the actions further comprise changing an attitude of the vehicle based on the bias adjusted directional rotational rates. 
     
     
         14 . The system of  claim 13 , wherein the changing comprises activating a thruster of the vehicle. 
     
     
         15 . The system of  claim 11 , wherein the estimate of bias of magnitude of momentum and the estimates of bias of directional rotational rates are further based on outputs of an internal momentum storage device. 
     
     
         16 . The system of  claim 11 , wherein the inertial measurement unit comprises a micro electro-mechanical inertial measurement unit. 
     
     
         17 . The system of  claim 11 , wherein the iteratively updating comprises iteratively updating using a Kalman filter. 
     
     
         18 . The system of  claim 11 , wherein the iteratively updating, the adjusting, and the providing are performed in real time. 
     
     
         19 . The system of  claim 11 , wherein the directional rotational rates comprise three-dimensional directional rotational rates. 
     
     
         20 . The system of  claim 11 , wherein the iteratively updating comprises iteratively updating using one of: a fixed gain filter, a batch filter, recursive least squares, H-infinity control, or moving horizon estimation.